This invention relates generally to dishwashing machines and in particular to a soil separator for a dishwashing machine which removes soil particles from the recirculating washing liquid in a dishwashing machine.
Conventional dishwashers, such as used in homes, include a tub defining a washing chamber, one or more racks mounted in the chamber for supporting dishes to be washed and a spray arm or other spray device from which water is sprayed on the dishes which are supported in the racks. The water, after being sprayed on the dishes is collected in a sump at the bottom of the chamber from which it is pumped to one or more spray arms by means of a recirculation pump. At the end of a washing cycle, a pump removes the waste water from the sump and delivers the water to the household sewage system.
A problem which has been encountered in such conventional dishwashers is that food soil particles which are washed from the dishes and which are suspended in the washing liquid are redeposited on the dishes during the washing process. The operational program of most such conventional dishwashers includes a drying operation which follows the washing operation. During the drying operation, heat is generally applied to the washed dishes whereby such redeposited soil particles are baked on the dishes, thereby making the soil particles difficult to remove.
It is therefore desired to provide an apparatus for removing soil particles from the dishwashing liquid in a diswashing machine so that only clean water is recirculated to the dishwasher spray arm.
Prior art dishwashing machines have provided various types of filtering devices for filtering soil from the recirculating washing liquid. U.S. Pat. No. 1,853,589, W. R. Walker, discloses a dishwashing machine having a sump portion in which soil accumulates during the dishwashing operation. A valve controls the discharge of the dishwashing liquid from the bottom of the sump upon completion of the dishwashing operation in order to remove the collected soil from the bottom of the sump at that time.
U.S. Pat. No. 3,322,285 discloses a filter for use in a dishwashing apparatus wherein the dishwashing liquid is passed through the filter to strain out the food particles. At the end of the dishwashing cycle, the filter is back-flushed to clean the filter and to flush the collected soil particles to the drain.
U.S. Pat. No. 3,807,419 discloses a dishwashing machine including a soil collecting receptacle located with its inlet above the normal level of the accumulated liquid in the dishwashing chamber, whereby the portion of recirculated washing liquid which flows down the back wall of apparatus is collected in the receptacle. Washing liquid collected in the receptacle overflows the receptacle and, as it does so, passes through a filter located in the path of the overflowing washing liquid whereby soil particles are trapped by the filter. The filter is washed by liquid impinging against it and the filtered out soil particles are collected in the receptacle. During the draining operation, the soil particles collected in the receptacle are flushed to the drain by routing washing liquid through the receptacle to the drain. A valving mechanism is provided whereby the washing liquid which flushes out the receptacle pressurizes the receptacle and closes the valve while opening a drain valve, thus permitting the washing liquid and collected soil particles to pass to the dishwasher drain.
U.S. Pat. No. 4,243,431 discloses a dishwashing machine including a by-pass passage wherein a portion of the recirculating water flows through a chamber whereby soil entrained in the bypassed liquid is separated. During the draining operation, the soil is flushed from the receptacle.
A problem with the prior art soil removal structures has been that soil is removed from only a portion of the recirculated dishwashing liquid. A further problem with the prior art dishwashers has been that the soil removal structure has been rather complicated and therefore expensive to manufacture. A still further problem with the prior art soil removal structure has been that many of these structures depend on the use of a filter which may become clogged with continuous use of the dishwashing machine.
It is therefore desired to provide a soil removal apparatus for a dishwashing machine which is simple, inexpensive to construct, and which can effectively remove soil from a substantial portion of the recirculated dishwashing liquid.